feat(ui): Worker-Menü "Update Claude CLI" führt claude update aus

Neuer Eintrag im Worker-Menü der Titelleiste, der die Claude CLI über
das konfigurierte claude_bin (ExecutableResolver, inkl. Shim-Handling)
mit `claude update` aktualisiert. Ausgabe/Fehler landen im Footer-Strip
(FlashFooterSuccess/FlashFooterError), Menüpunkt ist während des Laufs
deaktiviert. 5-Minuten-Timeout tötet den Prozessbaum.

src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs

@@ -680,6 +680,96 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
         if (RestartWorkerStatus == text) RestartWorkerStatus = null;
     }
 
+    private bool _updatingClaudeCli;
+
+    private bool CanUpdateClaudeCli() => !_updatingClaudeCli;
+
+    [RelayCommand(CanExecute = nameof(CanUpdateClaudeCli))]
+    private async Task UpdateClaudeCliAsync()
+    {
+        _updatingClaudeCli = true;
+        UpdateClaudeCliCommand.NotifyCanExecuteChanged();
+        try
+        {
+            var dto = Worker is null ? null : await Worker.GetClaudeBinAsync();
+            if (dto is null)
+            {
+                FlashFooterError("Update failed: worker offline.");
+                return;
+            }
+
+            var (success, message) = await RunClaudeUpdateAsync(dto);
+            if (success) FlashFooterSuccess(message);
+            else FlashFooterError(message);
+        }
+        finally
+        {
+            _updatingClaudeCli = false;
+            UpdateClaudeCliCommand.NotifyCanExecuteChanged();
+        }
+    }
+
+    private static async Task<(bool Success, string Message)> RunClaudeUpdateAsync(ClaudeBinDto dto)
+    {
+        var resolved = ClaudeDo.Data.Environment.ExecutableResolver.Resolve(dto.Value);
+        if (resolved is null) return (false, $"Update failed: '{dto.Value}' not found.");
+
+        var psi = resolved.IsShim
+            ? BuildShimUpdatePsi(resolved.Path)
+            : new System.Diagnostics.ProcessStartInfo { FileName = resolved.Path, ArgumentList = { "update" } };
+        psi.UseShellExecute = false;
+        psi.RedirectStandardOutput = true;
+        psi.RedirectStandardError = true;
+        psi.CreateNoWindow = true;
+
+        using var process = new System.Diagnostics.Process { StartInfo = psi };
+        var stdout = new System.Text.StringBuilder();
+        var stderr = new System.Text.StringBuilder();
+        process.OutputDataReceived += (_, e) => { if (e.Data is not null) stdout.AppendLine(e.Data); };
+        process.ErrorDataReceived += (_, e) => { if (e.Data is not null) stderr.AppendLine(e.Data); };
+
+        try { process.Start(); }
+        catch (Exception ex) { return (false, $"Update failed: {ex.Message}"); }
+
+        process.BeginOutputReadLine();
+        process.BeginErrorReadLine();
+
+        using var cts = new CancellationTokenSource(TimeSpan.FromMinutes(5));
+        var timedOut = false;
+        // On timeout: kill the tree, which unblocks WaitForExitAsync below and lets the
+        // async output readers drain/complete naturally (mirrors VerifyCommandRunner).
+        await using var ctr = cts.Token.Register(() =>
+        {
+            timedOut = true;
+            try { process.Kill(entireProcessTree: true); } catch { /* already exited */ }
+        });
+
+        await process.WaitForExitAsync(CancellationToken.None);
+
+        return timedOut
+            ? (false, "Update failed: timed out after 5 minutes.")
+            : SummarizeClaudeUpdateOutcome(process.ExitCode, stdout.ToString(), stderr.ToString());
+    }
+
+    private static System.Diagnostics.ProcessStartInfo BuildShimUpdatePsi(string shimPath)
+    {
+        var shim = ClaudeDo.Data.Environment.ExecutableResolver.BuildShimStartInfo(shimPath, new[] { "update" });
+        return new System.Diagnostics.ProcessStartInfo { FileName = shim.FileName, Arguments = shim.Arguments };
+    }
+
+    // Pure so a test can drive it with fake process output instead of spawning a real `claude`.
+    internal static (bool Success, string Message) SummarizeClaudeUpdateOutcome(int exitCode, string stdout, string stderr)
+    {
+        if (exitCode == 0)
+            return (true, LastNonEmptyLine(stdout) ?? "Claude CLI is already up to date.");
+
+        var detail = LastNonEmptyLine(stderr) ?? LastNonEmptyLine(stdout) ?? "";
+        return (false, $"Update failed (exit {exitCode}): {detail}");
+    }
+
+    private static string? LastNonEmptyLine(string text) =>
+        text.Split('\n').Select(l => l.Trim()).LastOrDefault(l => l.Length > 0);
+
     [RelayCommand]
     private void DismissBanner()
     {

src/ClaudeDo.Ui/Views/MainWindow.axaml

@@ -66,6 +66,8 @@
                         Command="{Binding RestartWorkerCommand}"/>
               <MenuItem Header="{loc:Tr shell.menu.usageMonitor}"
                         Command="{Binding OpenUsageMonitorCommand}"/>
+              <MenuItem Header="{loc:Tr shell.menu.updateClaudeCli}"
+                        Command="{Binding UpdateClaudeCliCommand}"/>
             </MenuItem>
             <MenuItem Header="{loc:Tr shell.menu.repositories}"
                       FontSize="{StaticResource FontSizeMono}"